Structure and formation method of semiconductor device structure with gate stack

2. The semiconductor device structure of claim 1, wherein the first layer is U-shaped, the second layer is U-shaped, and the work function layer is U-shaped.

3. The semiconductor device structure of claim 1, wherein the second layer directly interfaces the high-k dielectric layer.

4. The semiconductor device structure of claim 3, wherein the first layer directly interfaces a top surface of the second layer.

5. The semiconductor device structure of claim 1, wherein a barrier layer is disposed between the first layer and the work function layer.

6. The semiconductor device structure of claim 5, wherein the barrier layer includes at least one of TiN or TaN.

10. The semiconductor device structure of claim 8, wherein the halogen element is chlorine or bromine.

11. The semiconductor device structure of claim 8, wherein second layer includes nitrogen.

12. The semiconductor device structure of claim 8, wherein the first layer and the third layer are a same composition.

13. The semiconductor device structure of claim 8, wherein the second layer interfaces a top surface of the first layer and interfaces a bottom surface of the third layer.

15. The semiconductor device structure of claim 14, wherein the first metal and the second metal are a same metal element.

16. The semiconductor device structure as claimed in claim 14, wherein the first metal, the second metal, and the third metal are a same metal element.

17. The semiconductor device structure as claimed in claim 14, wherein the second layer further includes oxygen.

18. The semiconductor device structure as claimed in claim 14, wherein the first layer further includes a halogen element.

19. The semiconductor device structure as claimed in claim 14, wherein the halogen element is fluorine.

20. The semiconductor device structure of claim 10, wherein the second layer further includes oxygen.